"Release the position !" is a stipulation used for many
retro-problems. It also appears in other forms: "Solve the position
!", "Open the North-East cage !"etc.
In essence, this stipulation asks you to find how a given (usually
quite tangled) position can be reached legally. So that it really asks
for a proof game but without insisting on
giving all painful details of a proof game. You "only" have to find
the tricky maneuver that is required to lock everything the way it appears
in the diagram. The remaining details need not be spelled out.
With the word "release", the "Release the position !"
stipulation emphasizes the kind of backward reasoning retro-solvers
often use when they start from the diagram position and play backward
moves (we call this "retracting") trying to reach the starting position.
They usually stop this retraction process as soon as they are confident
that no difficulty remains.
There are many such examples of this process among the detailed solutions
of problems from this WWW RetroCorner, but here is one more:
Die Schwalbe, 1969
13+12. Release the position !
Cleraly, the point of almost all retrograde analysis is indeed to
find how a given position can be reached legally, so that "Release
..." could be some kind of universal stipulation.
However, when they find it possible, retro-composers prefer more specific
stipulations like "Mate in 1"
that looks like a joke/trap, or e.g. "First move of the Bl. Queen?"
that you cannot answer if you miss some part of the unlocking mechanism.
In general, the "Release .. "stipulation is only used when
nothing else will do.